Hi guys, I'm planning on upgrading my standard lens which is an 18-55mm to an 18-250mm which is a great walk around lens since I sometimes do urban photography. I'm basically stuck between 3 companies, Tamron, Sony and Sigma. Which company do you think produces great quality pictures from a walk around good lens. I'm pretty meticulous when it comes to picture detail, so please give me your best advice.

The Sony/Tamron lenses are practically the same, with some minor differences in external styling. The lens elements are the same, so tools like DXO use the same optical corrections for both lenses. Some have said that the Sony focuses a little faster than the Tamron, but I've only ever had the Sony version of the lens so I can't say for certain. The Sony lens is rather decent, expecially for a superzoom.

I've not used the Sigma, but it comes with a HSM motor meaning that it should focus faster and quieter than the Sony. That could make it a very attractive option so if you can find a shop that stocks it, you could go have a play with the lenses to see which one works best for you.

Ooh, I overlooked that part about the Sigma version being HSM. For some reason I thought they also had an older non-HSM model too, which on checking again they didn't. That changes things a bit, as that lens has built in OS too, which can be used instead of that provided by the body.